I am working with an SMT part that has a large GND pad in the middle. It requires this ground pad to be soldered to a larger copper pour region for heat spreading purposes.
I designed the footprint in the footprint editor and placed it on my PCB. Then I drew the required copper pour region around the GND pad. What I see in the PCB editor is this:
I am confused by the black region surrounding the ground pad (indicated by the green arrow, which was drawn by me, not Kicad). Is this a region of solder mask surrounding the pad? It does not disappear when I hide the F.Mask layer, so Iâm not sure what it is.
As a new user, I wasnât able to include a second image in my first post. But I want to add this to the question.
The display in PCB Editor gets even weirder when I switch the copper pour fill from âSolid Fillâ to âHatch Pattern.â In Hatch Pattern, a bunch of black boxes appear inside the copper pour zone:
The black stuff is ânothingâ / âvoidâ / âBackgroundâ.
You may as well be watching next to your PCB.
The thin black line around the pad is called a âthermal reliefâ. It is an interruption of the copper, and itâs use is to make it easier to solder the pad to the GND plane.
Thermal viaâs are a part of the zone properties:
If you want to use the copper zone as a heat sink, then you have to turn off the thermal vias. By default this is done with the copper zone, but you can override this by setting it for a footprint, or for a single pad.
The hatch pattern, is a hatch pattern. A solid fill usually is better. Hatch patterns are a bit out of fashion these days. In the old days there were problems with making PCBâs flat if there was a great imbalance in the amount of copper between the top and bottom layer. The hatch patterns were invented back then to still have a reasonable GND (or power) plane, while still having approximately the same amount of copper on both the front and back layers, and thus to reduce warping during production.
Edit:
Thermal via â Thermal relief. Blame it on the keyboard, It was not me, the buttons moved.
Thanks for the reply. Everything youâre saying makes sense.
(âThermal viaâ means something different to me. Thermal vias, in my world, refer to small holes you drill to connect from the front copper and the back copper layers to spread the heat from the IC package to more copper surface area. I actually do plan to add about 35 thermal vias inside that big GND pad, but I havenât gotten around to that yet.)
Since I do want to use the pad as a heat sink, should I turn off âThermal reliefâ entirely as suggested in your image?
Is there a benefit to the 45 degree angle, @straubm?
The image you show looks hard to solder because paste applied to the 2-GND pad is going to spill out those big thermal relief spokes during reflow, no?
Itâs normal that solder paste distributes a bit around a pad and the connection of a footprint. Itâs also a combination with the solder mask layer that prevents the solder from spreading too far, and the solder stencil aperture (and thickness) that defines how much paste is deposited in the first place. Those things have to be balanced.
45 degree angle usually does not matter much. Sometimes there is an unfortunate interference with other things around the pad, and rotating the spokes can then be used to improve the connection.
The image was certainly âjust to show possible effectâ.
Changing the relief spokes angle will change noting to it what you are speaking about.
Past will not spill out as thermal relief spokes are covered by solder mask.
When clicking at my ID at top of the message second left click does nothing for me
When clicking at my ID at top of the screen second left click hides what was opened by first one.
I landed in information about me with Activity tab opened.
I donât see there any information about what to do to promote myself.
Do the new users have there some description of what they have to do to promote themselves?
The link I placed in my reply shows what is required by Rust to be come âBasicâ . Clicking on his ID shows his activity, so he can see what he needs to do to promote himself to Basic.
Rust needs to read 19 more posts and open 4 more topics to become Basic.
Piotr cannot be promoted, he has reached the top of the heap already!
The link I placed in my reply to Rust is here. It is a link to the FAQ for new members. It is often easier for new members to promote themselves than wait for Admin to arrive.
According to what I have tested till now.
When I open with that method my information I land with Activity tab active and donât see the needed information.
When I open someone else information I land with Summary tab open and see what is needed to compare with data from FAQ.
It was clear (from the beginning) that FAQ tells what are the tasks to be done (I know that FAQ exists), but as I have previously tested what you said only at my ID (so not seeing a Summary) it was not clear for me that you only write about two left clicks and nothing about that then you should select Summary.
May be you just didnât noticed that if the user clicks his own ID he donât see Summary at once or may be it works differently for you and me. May be something else (Cookies) decide with what tab the personal information page is opened.
